Hi Lucie,
Strollers are available for rent at a variety of locations throughout the Disney Theme Parks, Disney Water Parks and the Downtown Disney Area. Quantities are limited and subject to availability.
The current stroller rental fees (although always subject to change without notice) are:-
$15.00 USD per day for a single-passenger stroller
$31.00 USD per day for a double-passenger stroller
For Guests who require a stroller rental for multiple days, a length of stay rental ticket is available where you make a one-time payment transaction for as many days of rental as you will need. Upon visiting a Disney Theme Park, show your receipt at the stroller rental location and you will be expedited through the queue with a reduced wait time.
The current multiple day rental fees (although always subject to change without notice are:-
$13.00 USD per day for a single-passenger stroller
$27.00 USD per day for a double-passenger stroller
You can find out more information on stroller rentals on the Walt Disney World website
HERE
Wishing you a magical trip!